Impact energy absorbing member

ABSTRACT

The present invention is an impact energy absorption member that is characterized by comprising a long member of fiber reinforced resin having a lengthwise direction and a thickness direction, wherein the ratio of the thickness t (mm) of the long member to the length L (mm) thereof is within the range of 1/11000 to 6/1000 as well as the direction of an external force is substantially in agreement with the thickness direction of the impact member. The member of the present invention sufficiently absorbs impact energy from a moving body when collision occurs and greatly increases safety to collision of transportation equipment, for example, a motor car and the like as well as is light in weight and compact, whereby the member can improve resistance against environment and saves energy. Further, when this member is applied to a house and a building against which the transportation equipment may collide, it can reduce the loss of social properties.

DESCRIPTION

[0001] 1. Technical Field

[0002] The present invention relates to an impact energy absorptionmember used to absorb impact energy to prevent the damage oftransportation equipment by absorbing impact energy generated in thecollision thereof, the transportation equipment including vehicles suchas a passenger car, a track, and the like, airplanes such as a passengerplane and the like, vessels such as a fishing boat, a ferry boat, andthe like, railroad cars such as an electric car, a monorail car, and thelike.

[0003] 2. Background Art

[0004] Transportation equipment such as vehicles, motor cars, and thelike which has a possibility of collision while it moves is providedwith an impact energy absorption mechanism for protecting an equipmentmain body and the life of crews from the impact generated in thecollision. A hollow metal frame, a polymer-formed material, and so on,for example, have been used as a conventional impact energy absorptionmember.

[0005] Incidentally, a mechanism in which the conventional impact energyabsorption member absorbs energy is such that a metal- or polymer-formedmaterial receives an impact force, is deformed by compression orbending, and absorbs impact energy through the subsequent plasticdeformation or breakage thereof.

[0006] For example, Japanese Unexamined Patent Application PublicationNo. 9-2178 proposes an impact absorption structure for the interiormember of motor cars for absorbing impact by that a rib portion ispressed and deformed by being bent. The publication exhibitscharacteristics such as an elastic modulus in bending, Izod strength,and the like.

[0007] Further, Japanese Unexamined Patent Application Publication No.9-95197 proposes an energy absorption structure for the side portion ofa vehicle body capable of effectively absorbing energy in such a mannerthat a rib portion is elastically deformed and a load sequentiallyincreases accordingly. The publication further describes a shape havinga hollow portion.

[0008] Furthermore, Japanese Unexamined Patent Application PublicationNo. 5-32147 proposes an impact energy absorption member for a bumperusing a fiber-reinforced composite material. The mechanism of thecomposite material is such that when the material is deformed bycompression, it is exfoliated and broken so that energy to be absorbedthereby increases.

[0009] However, since the conventional impact energy absorption membersutilize plastic deformation and breakage due to compression as describedabove, the wall thickness of a member cannot help being increased, thatis, the member cannot help being formed in a bulky shape such as ahollow shape together with an increased wall thickness in order toabsorb a large amount of energy which is generated in collision at ahigh speed. Thus, these conventional impact energy absorption membersare disadvantageous in that the space of a cabin of transportationequipment is reduced and the dwelling property thereof is scarified andfurther the overall weight of the impact energy absorption membersincreases and gas mileage is lowered, which is undesirable from aneconomical and environmental viewpoint.

[0010] In contrast, the transportation equipment is required to greatlyreduce its weight from the view point of administration for protectingenvironment. It is expected to apply a sophisticated composite material,that is, a fiber-reinforced composite material (hereinafter, abbreviatedas FRP) that seems to greatly reduce a weight and to improve durabilityas a material to be replaced with a metal material. However, the FRP isa material that does not almost exhibit plastic deformation and hascompression and bending strength which is almost the same as that of themetal material while the FRP has tensile strength that is larger thanthat of the metal material. Therefore, it is difficult to actually usethe FRP at present because the FRP does not have a sufficient merit inthe reduction of weight in the conventional impact energy absorbingmechanism which is broken in the compression and bending modes.

[0011] Accordingly, a first object of the present invention is toprovide a light and compact impact energy absorption member that makesuse of the aforementioned bending and compression modes and caneliminate the drawbacks of the conventional heavy and bulky impactenergy absorption member for transportation equipment and sufficientlyabsorb impact energy from a moving body in the occurrence of collision.

[0012] In particular, it is an urgent matter to establish compatibilitybetween safety against collision from various directions and reductionin weight of an impact energy absorbing apparatus from the specialcircumstances in which motor vehicles for personal use occupy almost allthe portion of the transportation equipment. Thus, a second object ofthe present invention is to provide a means for solving the aboveproblem.

DISCLOSURE OF INVENTION

[0013] An impact energy absorption member of the present invention ischaracterized by comprising a long member of fiber reinforced resinhaving a lengthwise direction and a thickness direction, wherein theratio(t/L) of the thickness t (mm) of the long member to the length L(mm) thereof is within the range of 1/11000 to 6/1000 as well as thedirection of an external force is substantially in agreement with thethickness direction of the impact member.

[0014] When the impact energy absorption member of the present inventionis used, it is jointed and fixed mechanically and/or through bonding toportions where the member is desired to absorb impact energy such as theinsides of a door and a bumper, the inner surface and the externalsurface of a side panel, the rear portion of an engine, the periphery ofa cabin for crews, and the like.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015]FIG. 1 is a perspective view showing an embodiment of an impactenergy absorption member of the present invention;

[0016]FIG. 2 is a perspective view showing an embodiment of the impactenergy absorption member of the present invention which is differentfrom the impact energy absorption member shown in FIG. 1;

[0017]FIG. 3 is a perspective view showing an embodiment of the impactenergy absorption member of the present invention which is differentfrom the impact energy absorption members shown in FIGS. 1 and 2;

[0018]FIG. 4 is a perspective view showing an embodiment of the impactenergy absorption member of the present invention which is differentfrom the impact energy absorption members shown in FIGS. 1 to 3;

[0019]FIG. 5 is a perspective view of a pendulum impact test methodincluding a method of mounting an impact energy absorption member of therespective embodiments;

[0020]FIG. 6 is a perspective view showing an embodiment of the impactenergy absorption member of the present invention;

[0021]FIG. 7 is a perspective view showing an embodiment of the impactenergy absorption member of the present invention;

[0022]FIG. 8 is a perspective view showing an embodiment of the fixingportion of the impact energy absorption member of the present invention;

[0023]FIG. 9 is a perspective view showing an embodiment of the fixedportion of the impact energy absorption member of the present invention;

[0024]FIG. 10 is a perspective view showing a most preferable example inwhich the impact energy absorption member of the present invention isapplied to a motor car;

[0025]FIG. 11 is a perspective view when a door 4 in FIG. 4 is viewedfrom a compartment;

[0026]FIG. 12 is a sectional view in the direction of the arrow X-X ofFIG. 11; and

[0027]FIG. 13 is a perspective view of a pendulum impact test methodincluding a method of mounting the impact energy absorption members ofthe respective embodiments.

REFERENCE NUMERALS

[0028]1: long member

[0029]1A-1C: impact energy absorption member

[0030]2: lengthwise direction

[0031]3: thickness direction

[0032]4: fixing jig (pin)

[0033]5: support member

[0034]6: support member with bearing

[0035]7: reinforcing portion of long member

[0036]8: motor car

[0037]9: door

[0038]10: rotatable bar

[0039]11: connecting member

[0040] L: length

[0041] t: thickness

[0042] B: width

[0043] R: diameter of fixing jig

[0044] L1: entire span

[0045] L2: distance between pins

BEST MODE FOR CARRYING OUT THE INVENTION

[0046] Preferable embodiments of the present invention will be describedbelow with reference to the accompanying drawings.

[0047]FIG. 1 is a perspective view showing an embodiment of an FRPimpact energy absorption member according to the present invention.

[0048] First, the impact energy absorption member of the presentinvention is composed of an FRP long member having a lengthwisedirection and a thickness direction. The long member 1 is a generic termrepresenting members formed in a so-called sheet-shape, rope-shape, beltshape, and the like which are long with respect to a sectional area.Almost all the cross sections (lateral cross sections), which areperpendicular to a lengthwise direction, of these shapes are liable togenerate tension against an impact force. Of these members, thesheet-shaped member is particularly preferable. The lengthwise direction2 literally means a direction in which the length of the long member ismaximized, and the length is several tens of centimeters to severalmeters when it is a member used for motor cars. The lengthwise directionis not in coincidence with a direction of the impact force, and theimpact force is vertical to the lengthwise direction or has a certainangle thereto (θ of FIG. 5 to be described later). The thicknessdirection 3 is a direction approximately vertical to the lengthwisedirection and in approximate agreement with a direction in which thelong member is most deformed when it is subjected to the impact force.That is, the impact force itself is caused to be in substantialagreement with the thickness direction by tension even if it is notvertical to the lengthwise direction of the long member. Further, theFRP in the present invention is a fiber simple body which is composed ofreinforcing fibers such as carbon fibers, aramid fibers, glass fibers,and the like and formed in a braided-string-shape or in atwisted-fiber-shape or the fiber simple body partly impregnated withresin.

[0049] The ratio (t/L) of the thickness t (mm) to the length (L) of thelong member is within the range of 1/11000 to 6/1000. A so-calledsheet-shaped member having a thin thickness is preferable. The impactenergy absorption member of the present invention is disposed so thatthe direction in which the impact force acts is in substantial agreementwith the thickness direction. As described above, since the impactenergy absorption member of the present invention has a long size and athin wall thickness, even if the impact force acts thereon, it is notbroken by being bent or compressed so that it can absorb energy until itis broken by being extended (for example, as shown in the embodiment,when a carbon-fiber-reinforced composite material (hereinafter,abbreviated as “CFRP”) is compared with a high tension steel, the amountof energy absorbed by the CFRP is about ten times as large as thatabsorbed by the high tension steel and further the specific gravity ofthe CFRP is about one fifth that of the high tension steel, thus theCFRP has a very high weight reducing effect.). Breakage may be caused byelongation even at a value smaller than the above lower limit value.However, when the long member is used as a member for transportationequipment, the absolute value of the amount of energy absorbed by themember is not sufficient in this case. Further, the long member is notalways broken by being extended even at a value larger than the aboveupper limit value. The above ratio t/L is preferably 1/11000 to 3/1000,more preferably 1/4000 to 3/1000 and most preferably 1/3000 to 2/1000.

[0050] Furthermore, the impact energy absorption member of the presentinvention is a member substantially the entire cross section of which isdeformed by being extended when it is tested by a pendulum impact testmethod which will be described later.

[0051] The pendulum impact test method mentioned in the presentinvention is a scaled-up Charpy test method (refer to JIS-7111 andISO-179). As shown in FIG. 5, the endless long member 1 is stretchedaround pins 4 acting as fixing jigs fixed to a not shown highly rigidframe without looseness (pretension of 0.1 to 1 Kg is applied to thelong member 1). The pins at both the ends of the four pins have aninterval L1 which is equal to the length (entire span) of the longmember, and the remaining two pins have an interval L2 which is 80% ofthe entire span. Then, a columnar cone having a weight of 3 to 1 kN andR=200 to 100 mm is struck against the long member 1 at the center of thespan thereof at a speed at which the long member 1 is broken (the speedis adjusted at a height H from which the cone is swung). Note that theentering angle θ of the pendulum in this case is within the range of 30to 90°. The entering angle can be set by adjusting the positions of aframe and the cone.

[0052] The amount of absorbed energy is calculated by a method of anordinary Charpy test from the height to which the pendulum rises afterit applies impact to the long member 1. The height to which the pendulumrises also can be determined by recording the state of the pendulum by avideo camera. Specifically, the amount of absorbed energy E iscalculated by the following formula

E=½(WV ²)−Wgh

[0053] (g: gravity)

[0054] or,

E=Wg(H−h)

[0055] where, W shows weight of pendulum, V shows velocity, and h showsheight to which pendulum rises.

[0056] It should be noted that when the long member cannot directly befixed to the pins because it is difficult to process the long member inthe endless shape, the amount of absorbed energy can be measured byexecuting the pendulum test after connecting members (reference numeral11 of FIG. 13) are jointed to the long member by an adhesive or bolts sothat the long member can be fixed to the pins therethrough. At thistime, it is necessary that the connecting members and connectingportions be stronger than the long member so that breakage occurs not inthe connecting members and the connecting portions but in the longmember. Specifically, the connecting portions are composed of a FRPhaving high strength or a metal material. Further, when the long memberis too long, the length thereof can be adjusted by suitably cutting it.

[0057] At this time, it is preferable that the long member 1 of thepresent invention be deformed by being extended in the lengthwisedirection (extended) and tensile stress occur in approximately theentire cross section (cross section perpendicular to the lengthwisedirection, that is, lateral cross section). That is, the long member isdeformed in a direction where the length thereof increases on the sidethereof where impact is applied as well as on the side opposite to theabove side in the pendulum impact test. In general, when the long memberis deformed by being bent, an impacted side is compressed and anopposite side is extended. Whether or not the long member is deformed bybeing extended can be confirmed by directly bonding a strain gaugethereon and monitoring a change of strain while impact is applied to thelong member. Further, whether or not the long member is broken by beingextended can be confirmed by identifying a broken surface byfractography. In the FRP, a surface broken by elongation exhibits anaspect of great irregularity in which many fibers are fallen out andpulled out.

[0058] It is preferable that the impact energy absorption member of thepresent invention have an amount of energy absorbed per unit weight ofat least 3.9 J/g in the above pendulum impact test. When the impactenergy absorption member of the present invention has the amount ofenergy absorbed per unit weight of at least 3.9 J/g, it is made suitablefor transportation equipment and the like that are closely related togas mileage. As shown in comparative examples which will be describedlater, the impact energy absorption member of the present invention canabsorb energy per unit weight in an amount several times larger thanthat of the metal material. Note that the proper upper limit range ofthe amount of energy absorbed per unit weight of materials that can beused for the transportation equipment is about 50 J/g from a view pointof cost.

[0059] Further, the amount of energy absorbed per unit volume issuitably within the range of 5 to 40 J/cm³. Setting the amount withinthis range permits the effective space in the transportation equipmentto increase as well as the cost of the impact energy absorption memberto be accepted by the transportation equipment, which makes the impactenergy absorption member more preferable.

[0060]FIG. 1 is a view showing a thin sheet member acting as anembodiment of the long member 1. The sheet member has a length L (mm), awidth B (mm) and a thickness t (mm) and further has a lengthwisedirection denoted by reference numeral 2 and a thickness directiondenoted by reference numeral 3. An impact load (external force) actsapproximately in the thickness direction, that is, in a directionapproximately vertical to the longitudinal direction or at an angle θ(within the range of 30 to 90°) with respect to the longitudinaldirection. As mentioned later, the length, width, and thickness of thelong member 1 need not be always uniform. When the length, width, andthickness are not uniform, however, they will be represented by averagevalues.

[0061] The FRP in the present invention means fiber-reinforced resincontaining reinforcing fibers and matrix resin. The reinforcing fibersmainly bear the tensile load generated in a sheet member, and it is notalways necessary for the resin to cover all the fibers. That is, the FRPmay has portions composed only of the reinforcing fibers. The portionscomposed only of the reinforcing fibers has a feature that they are veryflexible and can be deformed along portions having a complex shape.

[0062] Used as the reinforcing fibers are fibers including inorganicfibers such as carbon fibers, glass fibers, alumna fibers, siliconnitride fibers, etc.; polyamide synthetic fibers such as aramid fibers,nylon, etc.; organic fibers such as aramid fibers, PBO (polybenzoxazine)fibers, polyolefin fibers, polyester fibers, polyphenyl sulfon fibers;and the like. These fibers can be used independently or in a mixture ofat least two kinds thereof.

[0063] The carbon fibers are particularly useful because they have highstrength and high elastic modulus and are excellent in corrosionresistance. The carbon fibers may be any of PAN (polyacrylnitrile)carbon fibers and pitch carbon fibers. Among them, however, PAN carbonfibers are preferable because they have a wide variation of theaforementioned elongation. When it is desired to provide the impactenergy absorption member with firmness, it is preferable to selectcarbon fibers having an elastic modulus of 200-600 Gpa, whereas when itis desired to provide the impact energy absorption member withflexibility, it is preferable to select carbon fibers having strengthwithin the range of 3 to 10 Gpa. When it is desired to maintain thestabilized shape of the impact energy absorption member for a longperiod of time, the carbon fibers can be preferably used because theyhave a less amount of creep deformation among the reinforcing fibers.For example, when it is required to apply pretension to the impactenergy absorption member from the relation thereof to a mounting portionwhich will be described later, the disposition of the carbon fibers inthe direction of tension permits impact energy to be effectivelyabsorbed. Further, it is preferable that the carbon fibers have adiameter of 5 to 15 μm to effectively exert tensile strength.

[0064] Further, glass fibers (in particular, fiber-like glass such as Eglass, C glass, S glass, etc.) are preferable because tensile strengthand compression strength are balanced therein. In the present invention,it is preferable that fibers have a diameter of 5 to 15 μm inconsideration of creep characteristics. When the fiber diameter islarger than this range, creeps are liable to be generated by a flaw on asurface. Further, the fiber diameter outside of this range reducesproductivity.

[0065] Aramid fibers that have high elongation and strength arepreferably used as the organic fibers. This is because that the aramidfibers have resistance to acid that is often used in the transportationequipment as well as have very high strength of 2.5 to 3.8 GPa so thatimpact energy can be absorbed with a small amount of them. Widely usedas the aramid fibers are Kevlar fibers. Since the specific gravity ofthe Kevlar fibers is smaller than those of the carbon fibers and theglass fibers, it can be used also when it is desired to reduce theweight of the impact energy absorption member. For example, when severalfibers of the reinforcing fibers, which are used in an impact energyabsorption member made of carbon fibers, are composed of Kevlar fibers,the weight of the impact energy absorption member can be more reduced.Further, since the organic fibers are non-conductive similar to theglass fibers, covering the carbon fibers with the organic fibers canentirely or partly make the surface of the impact energy absorptionmember non-conductive.

[0066] Any known shape such as a stand shape, a lobing shape, aspun-yarn shape, a woven-shape, a covering yarn shape may be employed asthe shape of the fibers. However, the strand shape and the lobing shapeare preferable to obtain an impact energy absorbing capability, that is,high tensile characteristics. Further, the rope and the like disclosedin Japanese Unexamined Patent Application Publication No. 11-302978 arealso preferable shapes.

[0067] The reinforcing fibers used in the impact energy absorptionmember of the present invention are disposed in a lengthwise directionof a sheet to absorb impact energy by tensile deformation. However, thedirection in which they are disposed need not be in strict agreementwith the lengthwise direction. Even if the reinforcing fibers aredisposed with a tilt of about ±5° with respect to the axis of the sheetin the lengthwise direction, they are regarded as being substantiallydisposed in the lengthwise direction when they are broken by a tensionmode. Nevertheless, fibers that are disposed in directions other thanthe longitudinal direction may be contained for the convenience offormation from the view point of productivity. The ratio of thereinforcing fibers disposed in the lengthwise direction to all thereinforcing fibers is preferably 70% or more and more preferably 80% ormore. For example, when an impact energy absorption member containingcarbon fibers is formed by drawing, organic fibers and glass fibers maybe disposed at portions in contact with a forming metal mold to reducethe wear thereof. Further, the application of twist of about 2 times/mto 10 times/m has an effect for suppressing breakage of strings, andthis is preferable in processing.

[0068] The reinforcing fibers are contained preferably in an amount of35 to 99 vol % and more preferably in an amount of 50 to 90 vol %. Notethat the fiber content can be measured according to JIS K7052.

[0069] Next, the matrix resin used in the present invention will bedescribed. Exemplified as the matrix fiber used in the present inventionare thermosetting resins such as epoxy resins, vinyl ester resins,unsaturated polyester resins, phenol resins, benzoxazine resins, etc.,thermoplastic resins such as polyethylene resins, polyamide resins,polypropylene resins, ABS resins, polybutylene telephthalate resins,polyacetal resins, polycarbonate resins, etc., and denatured resinsobtained by making these resins to alloys.

[0070] Polyvinyl chlorides are preferable because they are excellent ina low temperature performance. The epoxy resins, the polyester resins,vinyl ester resins, and the denatured resins thereof can be preferablyused as a material for the field of the transportation equipment becausethey are excellent in draw forming property as well as in chemical andweather resistance. Further, the phenol resins and the benzoxazineresins are preferable because they are excellent in noncombustibilityand generate a less amount of gas when they are burnt.

[0071] Further, when a recycle property and a shape application propertyare necessary, the thermoplastic resins such as the polypropylene resinsand the like can preferably be used.

[0072] Further, since the object of the matrix resins is not to exertcompression strength, rubber-like matrix resins having an elasticmodulus of about 20 MPa may be used. When characteristics other thanimpact absorbing characteristics are taken into consideration, it ispreferable that the elastic modulus of the matrix resins is within therange of 100 to 600 Mpa.

[0073] Next, the long member of the present invention may be of a sheetshape, a rope shape (FIG. 6), a belt shape, a wire shape, a chain shape,a net shape(FIG. 7), and a thin sheet shape as long as the entire crosssection thereof is deformed by being extended in the aforementionedpendulum impact test. However, an amount of deformation larger than acertain degree is necessary from the meaning of absorbing a largeramount of impact energy and reducing an impact load applied to a crew.Thus, it is more preferable that the curvature of the long member whenit is bent be 1 m or less. This is because that since an amount ofabsorbed energy is the product of a load (P) and an amount ofdislocation (S), when the amount of dislocation is made to one half inthe absorption of the same amount of energy, the load is doubled.

[0074] The curvature in bending can be measured by bending a member cutto 500 to 1000 mm at three points and geometrically determining thecenter of the curvature of the member from the photograph of the bentmember.

[0075] Further, the impact energy absorption member of the presentinvention is disposed so that a direction in which an impact force actsis in agreement with the thickness direction of the member. This isbecause that when the impact force acts on the impact energy absorptionmember, tension, that is, a drawing force acts on fibers disposed in thelengthwise direction. Note that fibers may be twisted each other(principle of rope) so as to increase the capability thereof for bearinga tensile load. More specifically, a rope, a belt, and a string-shapedmaterial can be exemplified as this arrangement. Further, it ispreferable that a sheet member form a closed loop to improve an energyabsorption performance.

[0076] The loop-shaped sheet member has a merit, as compared with asimply long sheet member the ends of which must be jointed to each otherby bonding or mechanically, that the weight of which can be reducedbecause it does not need a jig for jointing the ends and that the weightof which is not increased by the reinforcement that is applied to thesimple sheet in consideration of stress concentration. Further, theloop-shaped sheet also has a merit that a mounting job can be easilyexecuted when it is assembled or repaired. Furthermore, the continuousdisposition of reinforcing fibers along the loop permits tensilestrength to be exerted ideally. As a result, the loop-shaped member hasa merit that it can absorb impact energy in a very large amount.

[0077] Note that the width of the closed-loop-shaped sheet member neednot be constant and may be tapered as in the absorption member shown inFIG. 4. Further, the closed-loop-shaped sheet member may be separated toa fork-shape at an end as in the absorption member shown in FIG. 3. Morespecifically, a net-shaped absorption member having a plurality ofbranched portions as in the absorption member shown in FIG. 7 and agut-shaped absorption member having intersections are preferable.

[0078] Note that when the FRP is broken by being extended, therelationship among the tensile strength (σ), the elongation (e) and theamount of absorbed energy (E) of the FRP is approximately represented bythe following formula. Thus, it is preferable to select a materialhaving suitable strength and elongation according to a necessary amountof energy to be absorbed.

E=½(σe)

[0079] However, excessively large elongation in the transportationequipment results in an excessively large amount of deformation. In acase of, for example, a door of a motor car, there is a possibility thatan impact force reaches a crew when collision occurs on a side of themotor car. From what is mentioned above, it is preferable in thetransportation equipment that the tensile elongation in the lengthwisedirection of the FRP constituting an FRP member be within the range of0.3% to 3.5%. The tensile elongation is more preferably within the rangeof 0.5% to 3%. Note that the elongation of the FRP can be measuredaccording to JIS K7054 or JIS K7074.

[0080] Exemplified as the material having the suitable strength andelongation as described above are a carbon-fiber-reinforced compositematerial, a glass-fiber-reinforced composite material, and the like. Inparticular, reinforcing fibers having strength of at least 1.5 GPa arepreferable because the strength of the fiber-reinforced compositematerial can be improved by a smaller amount of the reinforcing fibers.

[0081] The impact energy absorption member of the present inventionspecifically find a wide range of uses in the general transportationequipment such as motor cars, which are generically called as anautomobile, track, trailer, passenger car, sports car, racing car, motortricycle, and the like as well as an airplane, motor bicycle, electriccar, cargo, vessel and the like.

[0082] Among them, one of preferable uses is a door for a motor car.When the sheet-shaped FRP impact energy absorption member of the presentinvention is mounted to a portion where a steel pipe called an impactbar is conventionally mounted, it can absorb impact energy generatedwhen collision occurred on a side of a motor car and protect a crew aswell as reduce the weight of the door. In a passenger car having aweight of about 1 ton, The sheet member of FIG. 2 that is composed of acarbon-fiber-reinforced composite material having a thickness of 0.5 mmand a width of 100 mm and formed in a closed-loop-shape is fixed to theframe of a door. Fixing jigs such as pins or the like are used as afixing method, and the fixing jigs are mechanically fixed to the frameas shown in FIG. 5. At this time, it is preferable that the frame bemore rigid than a conventional frame. The impact energy absorptionmember may be fixed after pretension is applied thereto to reduce anamount of substances which are generated in collision and enter a cabin.

[0083] As other uses of the impact energy absorption member in thetransportation equipment, it is installed between an engine room and acabin for the purpose of preventing engine parts from entering the cabin(passenger's compartment) or installed in the vicinity of fuel partssuch as a natural gas tank, hydrogen gas tank, gasoline tank, methanoltank, and so on for the purpose of preventing a fuel vessel from beingdamaged by an impact and causing fire and the like.

[0084] Further, it is also possible to make the portion where the impactenergy absorption member is fixed to the frame rotatable to ease thestress concentration at the fixing portion so as to suppress the earlybreakage of the frame in the vicinity of the fixing portion. As a methodof making the fixing portion rotatable, there are a method of causingthe member of the present invention to be in contact with a pin having alow coefficient of friction and making the member itself rotatable bylubricant (FIG. 8), a method of receiving a pin 6 fixed to a member bysupport members 6 each provided with a bearing to permit the member tobe rotated together with the pin (FIG. 9), and the like. Making thefixed portion rotatable enables only tension to act more effectively,whereby a larger amount of energy can be absorbed. Further, it iseffective for the increase of an amount of energy to be absorbed toincrease the strength of the portion in the vicinity of the fixedportion of a long member by increasing the amount of the reinforcingfibers used in the long member or by partly reinforcing the long member(7 in FIG. 9). In particular, the partial reinforcement can beeffectively applied to a portion where stress concentration is liable tooccur such as a portion where a curvature increases, a portion where thelong member comes into contact with other member, and the like.

[0085] As described above, while the impact energy absorption member ofthe present invention is the fiber-reinforced composite material, thecategory thereof is very wide and includes not only the so-called FRPhaving high rigidity and strength used for structure but also compositematerials used for a belt, rope, tire, and the like.

[0086] In shapes other than the sheet shape, a rope shape is preferablebecause it is excellent in an abrasion property (FIG. 6). Morespecifically, strand-shaped reinforcing fibers are arranged as abraided-cord-like fibers or a twisted fibers, and a rope is arranged bycombining these fibers. In the case of the rope shape, an end the ropemay be returned and caulked by metal fitting, may be subjected toSATSUMA-end knitting or the like, or may be fixed by being sewed with asewing thread which is a method called stitching. In addition to theabove, the end of the rope may be processed by screw-end clamp, eye-endclamp, jaw-end clamp, SHINKO clamp, end supported socket clamp, opentype socket, DINA anchor, and the like, similarly to a steel wire. Amongthem, when the end is processed by the screw-end clamp, the absorptionmember can be jointed to a vehicle body, a vehicle, and the like througha screw, which is suitable to assemble and disassemble them.

[0087] Further, as described below, a state without an end (endlessstate) may be provided by forming a rope or the like to a loop. In animpact energy absorption member formed in the loop shape, it is alsopreferable to reinforce the overlapped portion thereof by caulking itwith metal fitting or the like or by further winding reinforcing fibersaround the overlapped portion so that the entire cross section of theabsorption member can effectively bear a tensile load. It is needless tosay that the amount of the reinforcing fibers is increased or decreasedas necessary in portions other than the overlapped portion to reduce theweight of the absorption member.

[0088] As described above, in the impact energy absorption member of thepresent invention, fibers of high strength are subjected to breakage bytension that exhibits the highest energy absorbing efficiency so as toabsorb energy generated when an impact is applied to the absorptionmember. Accordingly, the impact energy absorption member can be utilizedalso as an installation type energy absorption member for protecting thetransportation equipment including motor cars as well as buildings andhouses against which the transportation equipment may collide from animpact. A specific example is an energy absorption member which is usedin place of a protection fence, a guard rail, and the like.

[0089] Next, a method of manufacturing the sheet-shaped impact energyabsorption member of the present invention will be described. Tomanufacture the impact energy absorption member of the presentinvention, all the technologies including a filament winding method, apulltrusion process, a pull/wind method, a hand lay up method, a resintransmolding method, and so on can be used. Among them, the pulltrusionprocess and the pull/wind methods are preferable because they cancontinuously manufacture a loop-shaped impact energy absorption memberin which reinforcing fibers are disposed in the longitudinal directionof a sheet by using a tubular metal mold, disposing fibers in the radialdirection of the tube and cutting the tube in round slices.

[0090] Further, the filament winding method also is a preferable formingmethod. For example, when the loop-shaped impact energy absorptionmember is manufactured, reinforcing fibers or reinforcing fibersimpregnated with matrix resin are wound around a mandrel having a crosssection corresponding to a desired loop shape and then entirely, partlyor additionally impregnated with matrix resin. Subsequently, the matrixresin is hardened on the mandrel or after it is removed therefrom,thereby obtaining a tubular member. Further, the tubular member is cutin round slices having a necessary width to thereby obtain the impactenergy absorption member of the present invention. Further, in theaforementioned draw forming method and the filament winding method,since reinforcing fibers are formed continuously around the entireperiphery of a loop, there can be obtained a most preferable impactenergy absorption member that has very high tensile strength and isuniform.

[0091] Further, a rope- and string-shaped impact energy absorptionmembers can be manufactured in such a manner that reinforcing fiberstrands or reinforcing fiber strands impregnated with resin are knittedor formed to a twisted structure using a braided-string manufacturingapparatus such as a braider, further a plurality of strands are twistedand impregnated with resin, and then the resin is hardened.

[0092] Next, an example to which various types of the impact energyabsorption members of the present invention are most preferably appliedwill be described.

[0093]FIG. 10 is a perspective view of a motor car 8 in which impactenergy absorption members 1A to 1C of the present invention are used,wherein the impact energy absorption member 1A is used to absorb impactenergy generated from a door; the impact energy absorption member 1B isused to absorb impact energy generated from an engine accommodated in anengine hood; and the impact energy absorption member 1C is used toabsorb energy generated in rear-end collision. Any of the embodiments ofthe impact energy absorption member of the present invention can beapplied to the above uses. Among these absorption members, the impactenergy absorption member 1A will be described in detail. FIG. 11 is aperspective view in which a door 9 in FIG. 10 is viewed from a cabin.The door 9 includes a pair of right and left rotatable bars 10 that arerotatably disposed on both the sides of the interior of the door 9 andthe impact energy absorption member 1A of the present invention that isstretched between the pair of rotatable bars 10. As shown in FIG. 12which is a sectional view in the direction of the arrow X-X of FIG. 11,the impact energy absorption member 1A is formed in an endless beltshape (the one shown in FIG. 2 described above) and stretched so as tosurround the pair of rotatable bars 10.

[0094] When the impact energy absorption member 1A arranged as describedabove is disposed on the inner surface side of the door 9, if impactenergy is applied by a traffic accident or the like in the direction ofthe cabin from the outside of the door, that is, if impact energy isapplied in the direction of a white arrow in FIG. 12, first, the impactenergy absorption member 1A receives the impact energy and converts itto cause the entire lateral cross section thereof that is perpendicularto the lengthwise direction thereof to be deformed by being extended. Inother words, the impact energy is converted into the deformation due toelongation of the entire cross section of the absorption member, and theimpact energy is resisted only by the tensile stress, different from aconventional impact energy absorption member that intends to absorbimpact energy through the partial plastic deformation thereof. As aresult, the impact energy absorption member 1A can absorb a very largeamount of impact energy. At this time, the rotatable bars 10 rotatefollowing the dislocation of the impact energy absorption member at theoccurrence of collision and uniformly disperse locally applied impactenergy to the entire cross section of the overall length of theend-belt-shaped impact energy absorption member 1A that has beendeformed by being extended, whereby a larger amount of impact energy canbe absorbed.

EXAMPLE 1

[0095] Carbon fibers were used as reinforcing fibers, and the strands of“Toreca” T700S (elastic modulus: 235 GPa, strength: 5 GPa, elongation:2.1%) supplied by Toray were impregnated with bisphenol A type epoxyresin and subjected to filament winding, and the resin was hardened inan oven at 130° for 2 hours. With this processing, impact energyabsorption members each composed of a closed-loop-shaped FRP sheetmember (containing the carbon fibers in the amount of 60 vol %) wereobtained. Each absorption member had a width of 50 mm, a thickness of0.3 mm, and a length of 100 mm. The tensile strength of these memberswas 2700 Mpa, and the elongation thereof was 2.1%.

[0096] An impact test of the sheet members was carried out by mountingthem on a home-built pendulum impact tester described in thisspecification and shown in FIG. 5 through four pins. As a result, thesheet members were broken by being extended and divided into pieces, andthe value of energy absorbed per unit weight of each sheet member was17.5 J/g. Further, when broken cross section were observed with ascanning type electron microscope (model: SEM-XMA S4000 made by HitachiCorp.) with magnification of ×5000, it was admitted that fibers wasdrawn out from the entire cross sections, whereby it could be confirmedthat they were broken by being extended. (Table 1) TABLE 1 Impact energyabsorbing material Physical properties in longitudinal Size directionResult of impact test Constitution Thick- Elonga- Amount of Form- Fiber-ness Width Length Strength tion Elastic absorbed ing reinforced Vf (t)(B) (L) (α) (e) modulus Weight energy (E) Joint Mode of method resin %mm mm mm t/L MPa % GPa g J/g J/cm³ method breakage Exam- FW Carbon 600.3 50 1000 0.0003 2700 2.1 135 24 17.5 28.4 Pin Drawing ple 1 fiberEpoxy Exam- FW Carbon 60 0.5 100 600 0.0008 2700 2.1 135 48 16.9 27.0Pin Drawing ple 2 fiber Epoxy Exam- Prepreg Carbon 58 0.1 100 10000.0001 2500 1.9 130 15 14.3 22.8 Pin Drawing ple 3 fiber Epoxy Exam-Hand Carbon 90 1.0 100 600 0.0017 2400 2.5 150 105 13.7 24.1 Pin Drawingple 4 lay-up fiber Vinyl ester Exam- Pull Carbon 70 1.0 65 1200 0.00082900 1.8 160 133 12.0 20.4 Bolt Drawing ple 5 wind fiber Poly- esterExam- Prepreg Carbon 55 2.8 100 1000 0.0028 1200 1.0 125 122 3.9 6.0 PinDrawing ple 6 fiber Epoxy Exam- FW Kevlar 60 0.7 40 1200 0.0006 2100 2.975 44 22.3 29.0 Pin Drawing ple 7 Epoxy Exam- Hand Glass 40 1.4 100 6000.0023 700 3.0 25 170 5.0 7.5 Bolt Drawing ple 8 lay-up fiber Vinylester Exam- FW Carbon 56 0.5 100 600 0.0008 950 0.4 320 54 4.2 7.5 BoltDrawing ple 9 fiber Epoxy Exam- Twisted Kevlar 99 5 5 1000 0.005 11003.0 — 26 5.5 18.8 Loop Drawing ple 10 fiber Epoxy Com- FW Carbon 60 2.2100 600 0.0037 2700 2.1 235 192 3.8 6.0 Bolt Bending parative fiberexam- Epoxy ple 1 Com- Steel pipe Wall Diam- 700 0.0014 1000 — 210 10400.4 3.0 Bolt Bending parative thick- eter = exam- ness = 30 ple 2 1

EXAMPLES 2-9

[0097] When sheet members were manufactured under the conditions shownin Table 1 and broken by the impact of a pendulum similarly to theexample 1, the values of absorbed energy shown in Table 1 were obtained.Further, when broken cross sections were observed with the scanning typeelectron microscope similarly to the example 1, it was admitted thatfibers was drawn out from the entire cross sections, whereby it could beconfirmed that they were broken by being extended.

COMPARATIVE EXAMPLE 1

[0098] When sheet members were manufactured similarly to the example 2except that a thickness was set to 2.2 mm and tested, they were brokenby being bent. At that time, the value of energy absorbed per unitweight was 3.8 J/g which was about one fourth that of the example 2.Further, when broken cross sections were observed with the scanning typeelectron microscope similarly to the example 1, fibers was drawn outfrom half of the cross sections, whereby it could be confirmed that theywere broken by being extended. However, the remaining half of the brokencross sections were covered with resin and almost no fiber was observed,whereby it could be confirmed that they were broken by being compressed.Thus, it could be confirmed that the sheet members were broken byso-called bending as a whole.

COMPARATIVE EXAMPLE 2

[0099] When steel pipes were tested with the pendulum impact tester inplace of FRPs, the pipes were broken by being bent. At that time, thevalue of energy absorbed per unit weight was 0.4 J/g.

EXAMPLE 10

[0100] Ropes each having a thickness of 5 mm were manufactured by way oftrial by twisting aramid fibers (Kevlar 49) of 3000 denier. Then, longmembers each having a length of 1000 mm were manufactured by bendingboth the ends of the ropes in a loop shape, impregnating the loopportions with room-temperature-hardening-type epoxy resin, caulking boththe ends with steel fitting of 1 mm thick, and hardening the epoxyresin. Subsequently, when each long member was mounted on the pendulumimpact tester and tested similarly to the example 1, it was broken bybeing extended. At that time, the value of energy absorbed per unitweight was 5.5 J/g.

Industrial Applicability

[0101] According to the present invention, a very superior andconventionally unobtainable impact energy absorption member that iseasily broken in a tension mode and excellent in impact energy absorbingcharacteristics regardless of that it is light in weight can beobtained, whereby a member for transportation equipment that isexcellent in impact resistance can be obtained.

1. An impact energy absorption member, characterized by comprising along member of fiber reinforced resin having a lengthwise direction anda thickness direction, wherein the ratio of the thickness t (mm) of thelong member to the length L (mm) thereof is within the range of 1/11000to 6/1000 as well as the direction of an external force is substantiallyin agreement with the thickness direction of the impact member.
 2. Animpact energy absorption member according to claim 1, wherein the longmember is formed in a sheet shape and the ratio t/L thereof is1/11000-3/1000.
 3. An impact energy absorption member according to claim1 or 2, wherein the impact energy absorption member is used fortransportation equipment.
 4. An impact energy absorption memberaccording to any of claims 1 to 3, wherein the impact energy absorptionmember is an installation type collision buffering member used for thetransportation equipment.
 5. An impact energy absorption memberaccording to any of claims 1 to 4, wherein substantially the entirelateral cross section of the long member is deformed by being extendedin a pendulum impact test method executed after an impact is appliedthereto as well as the amount of energy absorbed per unit weight of theabsorbing member is at least 3.9 J/g.
 6. An impact energy absorptionmember according to any of claims 1 to 5, wherein the long member is ofan endless shape.
 7. An impact energy absorption member according to anyof claims 1 to 6, wherein the elongation (e) in the longitudinaldirection of the fiber reinforced resin is within the range of 0.3 to3.5%.
 8. An impact energy absorption member according to any of claims 1to 7, wherein the tensile strength of the reinforcing fibersconstituting the fiber-reinforced resin is at least 1.5 GPa.
 9. Animpact energy absorption member according to any of claims 1 to 8,wherein the reinforcing fibers constituting the fiber-reinforced resincontain at least carbon fibers.
 10. An impact energy absorption memberaccording to any of claims 1 to 9, wherein the ratio of the reinforcingfibers that are disposed in the lengthwise direction of the long memberto all the reinforcing fibers contained in the fiber-reinforced resin isat least 80%.
 11. An impact energy absorption member according to any ofclaims 1 to 10 comprises the long member and a support member of thelong member, wherein the support member is rotatable according to thedeformation of the energy absorption member when an impact is applied tothe long member.
 12. An impact energy absorption member according to anyof claims 1 to 11, wherein the long member is of a rope shape or of awire shape.
 13. An impact energy absorption member according to any ofclaims 1 to 12, wherein the amount of energy absorbed by the long memberis at least 5 J/cm³.
 14. An impact energy absorption member according toany of claims 1 to 13, wherein the resin of the fiber-reinforced resincomprises thermoplastic resin.
 15. An impact energy absorption memberaccording to any of claims 1 to 14, wherein the long member is partlyreinforced.
 16. An impact energy absorption member according to any ofclaims 1 to 15, where the fiber-reinforced resin is formed by a filamentwinding method or a pull/wind method.